Rotary tools, such as boring and drilling tools, are commonly used to cut, remove, and shape material, such as metal, earth, and rock. Such tools commonly encounter and generate heat, vibration, various stresses, and other conditions that may effect the performance and safety of the cutting tool. These conditions are often monitored so that tool operators remain aware of the status of the tool. Also, tools themselves may have instruments mounted in them which may required input data for calibration or to vary the parameters to be monitored. Further, sensors and instruments on the tool may require electrical power for operation. Thus, there remains a need for a coupler that can relay data in full duplex between the stationary and rotary portions of the tool and can provide power to powered instruments on the rotating tool.
Matsushita et al., U.S. Pat. No. 4,837,556, disclose a system for transmitting power and data signals using an electromagnetic wave or light. The system is adapted to transmit power and information between stationary and moving portions of machines, such as spindles of numerically controlled machine tools. Data and/or power is transferred between an active module A to a passive module B. In the active module, data in parallel form is converted to serial form in a parallel to serial converter (P/S converter), frequency shift modulated, and amplified for transmission. This signal is then transmitted as an electromagnetic wave. Module A receives an optical signal from module B, converts this signal to an electrical signal, amplifies the electrical signal, and demodulates the signal to obtain serial data, then converts the serial data to parallel form in a serial to parallel converter (S/P converter) for further processing. The P/S converter and the S/P converter are controlled by a control timing signal CS.sub.1 generated by a controller comprising a microcomputer with reference to a suitable transmit/receive switch signal SR.sub.1. The passive module B receives the electromagnetic transmission from module A in a receiving head 13. A portion of the energy received is converted into a power supply voltage E.sub.1 in a rectifier and smoothing circuit 14. Another portion of the energy received is used to develop a baud rate clock signal by a frequency divider 15. The remainder of the energy received is demodulated by a detector 10 to provide serial data. As with the active module A, control of a S/P converter 11 for incoming data and a P/S converter 1' is provided by a controller 12' in response to an external control signal SR.sub.2. Thus, neither the active module A nor the passive module B is capable of duplex data transfer.
Peacock, U.S. Pat. No. 4,310,767, discloses a data interface for data transmission between rotating and stationary members. This system is specifically adapted for data transmission between an axle and a frame of a railroad car. A plurality of sensors detect stress which provide the strain gage transducer portion of a balanced bridge of a transducer circuit. Duplex data transmission is not possible in this configuration. A mode control actives a transmitter to activate a signal from the frame to the axle. The signal received at the axle serves to deactivate the bridge circuit using a relay or to enable logic circuitry in an amplifier to calibrate the transducers.
While Peacock shows a battery as the power source for the elements on the axle, he mentions that power could be provided by transmission between the frame and axle as by an air core transformer. Peacock provides no structure as to how this is to be accomplished.
Tanaka et al., U.S. Pat. No. 4,321,474, disclose another optical signal transmission system for communication between a rotating body and a stationary body. Tanaka et al. teach that multiple transmitting optical elements or multiple receiving optical elements can be used. This reference also teaches a parallel optical communication scheme (8 bits in the illustrated embodiment). Tanaka et al. show that information can be transmitted from the stationary body to the rotating body but does not suggest how this system can be adapted to accomplish simultaneous communication in both directions. Further, no power transmission between rotating and stationary bodies is suggested by Tanaka et al.
Einhorn et al., U.S. Pat. No. 4,753,506, teach no more than is shown in previously discussed references. Einhorn et al. disclose a transmitter and a plurality of beam splitters. This scheme creates a detection path so that a detector is always in communication with at least one transmission path from one of the beam splitters. Einhorn et al. provide no duplex communication or power transmission.
Thus there remains a need for a system which provides full duplex communication between rotary and stationary members along with means for coupling electrical power to the rotary member.